Everyone knows that a combination of diet and exercise is the best way to lose weight. But many of us have tried this, over and over again, without lasting success. Still, we know it’s important to take off those extra pounds, both for the sake of our physical health and our state of mind. Can diet pills help us meet our goals?

While pills are not a magic bullet that allows us to shed pounds effortlessly, a small minority of people do find them a helpful adjunct to a diet and exercise program. In a study of 2,800 people who lost at least 30 pounds and kept them off for over a year, only 4 percent did it with the use of medications. Another approach is to lose some weight and use medication to help keep the weight off.

While I’ve seen people helped with diet drugs in the short run, weight tends to bounce back after medications are discontinued, despite best intentions and efforts to maintain the hard-won weight loss.

I compare this phenomenon to a person who is diagnosed with high blood pressure and put on medications to bring it down. It works, but don’t expect the blood pressure to stay low when you go off the medications! It’s true for both blood pressure management and weight control: Our bodies have a strong maintenance system that’s difficult to override, even when it’s sometimes not in our best interest.

Limited prescription options

The Food and Drug Administration treats obesity drugs differently than it does other drugs. There are only two prescription drugs that are FDA-approved for longer-term use for weight loss (several others are approved only for short-term use over a few months). Both of the longer-term drugs are only recommended for people who are significantly obese.

Sibutramine (trade name Meridia) increases metabolism and affects serotonin and other neurotransmitters. People report they feel full and more energetic. Because it can increase blood pressure, it must not be used in people with hypertension, and blood pressure must be regularly monitored while using the medication. People with heart disease, stroke and heart rhythm disturbances must also avoid the medication, and it must not be used in combination with decongestants, bronchodilators (used for asthma) or MAO inhibitors (medications used against depression). It is not particularly effective in the long run. The FDA has found undeclared and unapproved sibutramine in some specific dietary supplements, which has prompted voluntary recalls.

Orlistat (trade name Xenical) has helped people to achieve only mild weight loss in studies. It blocks the action of lipase, an enzyme in the intestine that breaks down fat. As a result, 30 percent of fat eaten is not absorbed and is excreted in the stool. It sometimes causes gastrointestinal problems, including a lot of gas, an oily discharge and a frequent need to have bowel movements. The FDA also approved this drug at a lower dose for over-the-counter use by adults (under the trade name Alli). It was the first and only over-the-counter diet drug to win approval from the agency.

Beware over-the-counter remedies

There are numerous weight-loss remedies available over the counter. But let the buyer beware! Medications are medications, whether or not they are herbal, “natural” or under the jurisdiction of the FDA. I recommend that if you try any of these alternatives, you do so carefully. Don’t combine them with one another or with other medications, and most importantly, discuss them with your doctor. Many of them can have profound effects on your health in ways you might not predict. Some simply don’t work, despite testimonials where people are paid significant amounts of money for losing weight.

Here are some common — or once-common — over-the-counter dietary aids, including some that are now restricted:

Phenylpropanolamine or PPA, once also an active ingredient in decongestants. It has a mild appetite-suppressing effect that usually does not work for long. It should never be used with other decongestants and may cause elevated blood pressure and increase the risk for stroke. In the United States, PPA is no longer sold without a prescription after studies associated it with increased risk of stroke.

Ephedrine, ephedra or ma huang, a component in adrenaline. It can cause a rapid heart beat, increased blood pressure, and even psychosis and seizures. There have been some reported deaths attributed to its use. Do not use these products. After FDA banned PPA, many diet pill makers reformulated their products with ephedra. However, dietary supplements that contain ephedra have been banned in the U.S. since April 2004, after the FDA determined that ephedra posed an unreasonable risk to those who used it.

Chitosan, a component from shellfish that is touted as a “fat trapper.” I wouldn’t waste your money on this one: I have published three different studies that show that the only thing it traps is your money. For example, one study suggested it would take more than seven months to lose a pound of body fat via the effects of chitosan. For women, no fat was trapped.

Dietary herbal teas, which usually contain ingredients that work as laxatives. Over time, they can cause chronic pain and constipation. People then become dependent on their use for bowel movements. However, the Chinese used strong Oolong tea to “control weight” – about 1 ½ quarters a day.

Exercise is crucial, no matter what

While drugs may be part of the answer to a weight problem for a few people, there’s one method I’d recommend for everyone: exercise. It’s nearly impossible to maintain weight loss without it. And regardless of one’s weight, the other health benefits it provides are many.

Set your own goals. To help, wear a pedometer and record how many steps that you walk a day. If you walk 3,000 steps daily, try increasing it every week or two by about 500 steps, until you reach 8,000 to 10,000 daily. Don’t get discouraged. Once exercise becomes a habit, you’ll realize why it’s one “pill” you’ll want to swallow for the rest of your life.

Finally, a goal that doesn’t involve weight loss is “health at every size.” Linda Bacon, a researcher at UC Davis, has shown that if you listen to your body with respect to eating, being active and feeling good about yourself, it can improve your health without weight loss. It helps to have a support group.